The present invention relates to transferring items from an elevated supply stream to a container at a lower elevation. More particularly, the invention relates to a variable volume, height adjustable buffer for capturing and retaining a multitude of similar articles and then selectively batch dispensing the items into a container located at a lower elevation.
Although the present invention may be used in conjunction with a variety of items often found in a supply stream such as, for example, food products, building components and manufacturing components, the present application finds particular use with preforms. Preforms are typically formed of a thermoplastic and are the initial material for thin wall containers such as bottles for soft drinks, detergents, etc. produced with blow molding machines.
In one method of blow molding plastic containers, such as polyethylene terephthalate (PET) carbonated beverage bottles, a preform first is formed by injection molding followed by reheating and stretch blow molding of such preforms into containers. The preforms are generally cylindrical tubes having a hemispherical closed end and an opposite open end with a ring shaped shoulder and threaded sleeve. Superficially, preforms generally resemble test tubes having a threaded end.
Depending upon the size of the container to be blow formed, the preforms have different sizes particularly in length and wall thickness, whereas the diameters are somewhat standardized with reference diameters being 22, 28 and 38 millimeters, measured on the outside of the thread.
The preforms are injection molded in large numbers at an injection molding machine, which includes a preform cooling or handling plate. After the preforms are removed from the injection molding machine, they are brought to an elevated position by a conveyor belt and then delivered by a chute to a large corrugated board box normally identified as a xe2x80x9cgaylordxe2x80x9d for storage and shipment. The preforms merely drop from the chute and into the gaylord. Since a gaylord may be four or more feet tall and the chute discharge is at a still higher elevation, the drop from the chute to the bottom of the gaylord may be five feet or more.
Surface damage of the preform typically occurs during dropping through such distances into the gaylord. Such damage is manifest by scratching or scuffing of the surface of the preform and in an extreme case in the chipping of a threaded surface. Since this damage occurs during loading of the articles which is after inspection, the damage often goes undetected. Consequently, such defects on the exterior surface of a preform result in a blow-molded container having an unacceptable surface contusion.
A number of methods have been applied to reduce the surface damage to preforms prior to the final blow molding process.
Specifically, U.S. Pat. No. 5,509,965 discloses immediately coating preforms after the injection molding of such preforms to prevent damage of the preforms by engagement with one another.
However, such processes typically require additional materials as well as processing equipment, thereby adding to the cost.
Accordingly, a need exists for a system that can transfer, with a minimum of damage, preforms from the injection mold supply stream at a higher elevation and into a container at a lower elevation for storage and subsequent transport.
The need further exists for a such a system for loading a multitude of similar articles into relatively deep containers that minimizes damage to the articles particularly where the articles are dropped from a relatively high elevation relative to the bottom of the container.
There is a yet further need for such a system for loading a multitude of similar articles into a deep container wherein the drop or fall distance into the container is kept relatively constant regardless of the container height.
In accordance with the present invention, a vertically oriented buffer is positioned between the discharge of a chute and the bottom of the gaylord. The buffer establishes and maintains a relatively constant drop height so the preforms only drop a short distance into the buffer. In this respect the buffer has expandable sides that allow the base of the buffer to move from a higher elevation to a lower elevation. As preforms accumulate and pile onto the base of the buffer, the buffer sides expand downwardly. In this fashion the base is lowered so the top of the pile of preforms remains at a substantially constant elevation relative to the discharge end of the chute.
The buffer is sized and positioned to fit within the gaylord so that as the base is lowered, it extends into the gaylord. When the base of the buffer is at or near the bottom of the gaylord an opening in the base is created so the preforms can be dispensed into the gaylord. The buffer is collapsed by raising the base and this results in a controlled dispensing of the preforms into the gaylord through the open base.
Accordingly, the present invention may be characterized in one aspect thereof by an apparatus for maintaining a relatively constant drop distance during the filling a container having an open top and a closed bottom with a multitude of similar articles from a source located at a higher elevation, the apparatus including:
a) a vertically expandable buffer disposed intermediate the elevated source and the container for receiving the articles directly into the buffer from the elevated source;
b) a top frame at a fixed location defining a buffer inlet;
c) a bottom frame defining a buffer outlet including a gate closing the outlet, the bottom frame being sized to fit into the container and being movable between an elevated position adjacent the top frame to a lower position, the bottom frame at the onset of filling being at the elevated position disposed a defined vertical distance below the elevated source that defines an initial drop distance of articles falling from the source and into the buffer;
d) expandable sides connecting the top and bottom frames;
e) control means for controlling the descent of the bottom frame in response to the entry of articles into the buffer that fill the buffer to a fill level for maintaining a distance between the fill level and the source that is substantially equal to the initial drop distance; and
f) means opening the gate responsive to the positioning of the bottom frame at the lower position.
In another aspect the present invention may be characterized by a method for filling a container with a multitude of similar articles comprising:
a) dispensing the articles from an elevated source and through a defined drop distance into an expandable buffer disposed below the source and above the container;
b) expanding the buffer downwardly and into the container as the buffer is filled with the articles so as to maintain substantially the defined drop distance; and
c) opening a gate in the buffer when the buffer is expanded to a selected lower level for dispensing the articles into the container by dropping them from the buffer and the distance dropped from the buffer into the container being no greater than the defined drop distance.